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Positions, Structures and Polarization of 404 Compact Radio Sources
Accurate positions of 404 compact radio sources used as calibrators by the VLA
are presented. In addition, the structure and polarization of each source
at both 4885 and 1465 MHz are given. Eighty-five percent of the scurces
have spectral indices flatter than 0.5; all these are dominated by an
unresolved core. Half of these flat-spectrum sources contain nearby,
associated diffuse structure at a level exceeding ~0.4 % of the core
brightness at 20 cm.
Amplitude calibration was based on 3C286, whose fluxes at 4885 and 1465 MHz
were assumed to be 7.41 and 14.41 Jy, respectively, in accord with the
scale of Baars et al. (1977).
short description of columns, as taken from the publication:
- 1 source name
- 2 alternate name (3C, 4C)
- 3 Right ascension (B1950)
- 4 Declination (B1950)
- 5 Flux at 4885 MHz (mJy)
- 6 Flux at 1464 MHz (mJy)
- 7 Spectral index alpha^20_6, defined by S~(nu)^(-alpha)
- 8 Polarized flux at 4885 MHz (mJy)
- 9 Position angle of polarized flux at 4885 MHz in degrees
- 10 Degree of polarized flux at 4885 MHz, in percent.
- 11 Polarized flux at 1465 MHz (mJy).
- 12 Position angle of polarized flux at 1465 MHz in degrees
- 13 Degree of polarized flux at 1465 MHz, in percent.
- 14 Peak brightness of secondary structure, or upper limit
(as percentage of peak), at 6 cm.
- 15 Peak brightness of secondary structure, or upper limit
(as percentage of peak), at 20 cm.
- 16 Optical identification
- 17 Visual magnitude of optical ID.
- 18 A plus sign indicates that the optical ID was taken from
Hewitt and Burbidge 1980, ApJS 43, 57.
- 19 Note to structure (see other table) for sources marked with
Important comments concerning Table II follow.
Column 2. It is often difficult to decide whether a
given 4C source is to be identified with a compact
source. A conservative approach has been used.
5 and 6. This is the flux of the core in all cases where
this can be determined. Sources where this could not be
done have an asterisk in column 14 or 15. The error in
the flux is estimated to be less than
~ sqrt [(0.03S)**2 + (0.002)**2] Jy, with S in Jy.
8, 9, 11, and 12. The listed flux applies to the core
only, unless the core cannot be distinguished, in which
case the listing applies to the whole source. The error in
polarized flux is estimated to be sqrt [4 + (0.4S)**2] mJy,
where S is the total flux in Jy. The error in position angle
is strongly dependent upon the polarized flux, and is
roughly given by 65 sqrt[4 + (0.4S)**2]/m degrees.
14 and 15. Listed secondaries are generally found within the
clean-search window defined earlier. Occasionally, larger windows
were searched to find more distant structure. The absence of a
listed secondary does not guarantee the source has none -it may
lie outside the search window. This is particularly true at 6 cm
where the search window was 6.4 arcsec wide. Entries marked
by an asterisk indicate the source is slightly resolved, but
not enough for a reliable map.
16-18. These are taken from Hewitt and Burbidge